The present invention refers to an air flow controlling device to be used in refrigerators and freezers, in which the evaporator may be provided isolated from the refrigeration compartment, and particularly in those appliances in which the refrigeration of any refrigerated compartment is obtained by forced air circulation and the defrost is automatically made by natural convection.
In the refrigeration appliances, particularly those of the xe2x80x9cno frostxe2x80x9d type, in which, the freezing and refrigerating compartments are refrigerated by forced air circulation, the temperature in the compartments is controlled by a thermostat provided, for example, adjacent to an evaporator and which determines the switching on and off of the compressor, upon detecting the respective maximum and minimum temperatures of a temperature interval previously determined as the ideal operational temperature interval of at least one of the freezing and refrigerating compartments.
The refrigeration of the freezing and refrigerating compartments of these appliances is obtained by forced air circulation through the evaporator towards said compartments, by actuation of a fan.
In a known solution, in at least one of the ducts which connects the evaporator to a respective freezing or refrigerating compartment, there is provided a thermostatic valve, which selectively interrupts and permits the fluid communication between the respective compartment and the outlet of the evaporator.
In the known constructions of a thermostatic valve, said valve has a movable vane, which opens or closes the air passage, in order to regulate the temperature of the respective freezing or refrigerating compartment detected by a sensing bulb of said thermostatic valve provided in this compartment. In the closing operation of the vane of the thermostatic valve, said vane interrupts the flow of cold air from the evaporator to the respective compartment.
In this construction, when it is necessary to refrigerate only one compartment, the thermostatic valve thereof is commanded to present an operational condition, so that the respective compartment receives cold air from the evaporator.
Besides using one or more thermostatic valves of a relatively complex construction, this solution allows, at the inlet region of the evaporator, i.e., at the fan region, the mixture of the air flows from the compartments of the refrigeration appliance, which usually have very distinct temperatures. Said mixture of air masses with a high temperature differential results in energetic losses for the refrigeration system.
An alternative to avoid this mixture of air masses at different temperatures is to duplicate the circuits and the active equipments (fans, evaporators). When the refrigeration appliance has more than one forced air circuit, for example, such as described in the copending patent application, of the same applicant, filed on Jun. 21, 1999, with the title xe2x80x9cAn Automatic Defrost System for a Refrigerating Devicexe2x80x9d, it is also required to provide, in each circuit, a respective thermostatic valve, said valves being controlled by a control unit, in order to guarantee a desired operational synchronism between said forced air circuits.
However, these solutions increase the amount of components in the refrigeration circuit, affecting the maintenance, the arrangement of the inner space in the cabinet of the refrigeration appliance, besides increasing the final cost of the product.
It is a general objective of the present invention to provide an air flow controlling device for refrigerators and freezers, with a simple construction and practical installation, which allows to selectively interrupt and establish the fluid communication between the evaporator and each refrigeration compartment of the refrigerator or freezer, either in a refrigeration or in a defrost condition.
This and other objectives are achieved by an air flow controlling device for refrigerators and freezers, comprising at least two air flow heating environments and an evaporator positioned externally to said air flow heating environments and in selective fluid communication therewith, said device comprising, for each air flow heating environment, an inlet nozzle in fluid communication with the respective air flow heating environment, and an outlet nozzle in fluid communication with the evaporator and a respective obturator, which is operatively associated with the inlet and outlet nozzles and affixed to a respective shaft portion rotating between opening and closing positions, respectively permitting and blocking the fluid communication between said inlet and outlet nozzles, said shaft portions of the obturators forming a single common shaft, which is rotatively driven by a motor unit commanded by a control unit.